This is actually what triggered me to get the personal site license when it first came out a number of years ago.

JetBrains announces that IntelliJ is going Open Source.

I checkout the code, build it (~20ish minutes) inside of the downloaded bits, launch the newly compiled IDE, build the repo source again this time debugging IntelliJ from within itself. All in less than an hour, with no hiccups. Amazing.

I love JetBrains so damn much it hurts.